1. Technical Field
The present invention relates to a recording apparatus for feeding and transporting a medium and recording an image on the transported medium, and a medium transporting method.
2. Related Art
In the related art, a printer which is a known example of a recording apparatus includes an auto sheet feeder (hereinafter, referred to as ASF) (for example, see JP-A-2005-96450). When a printing operation starts, a sheet of paper stored in the ASF is fed by the driving of the ASF and a front end of the sheet is automatically positioned at a printing start position.
The ASF starts the feeding of a next sheet after a previous sheet has been fed and ejected. However, in this feeding method, since the feeding operation of the next sheet starts after the previous sheet has been ejected, a gap between the previous sheet and the next sheet exists and a standby time is present between the completion of a printing operation of the previous sheet and the start of a printing operation of the next sheet. Accordingly, a printing time is increased.
In order to solve this problem, JP-A-2005-96450 discloses a printing apparatus (recording apparatus) for simultaneously performing an ejection operation of a previous sheet and a feeding operation of a next sheet to reduce a standby time between the completion of a printing operation of the previous sheet and the start of a printing operation of the next sheet. According to this printing apparatus, it is possible to improve printing throughput.
JP-A-2005-96450 discloses a configuration in which a plurality of transport rollers are driven by respective motors. The transport of the next sheet (a recording sheet of a next page) starts after a rear end of the previous sheet (a recording sheet of a current page) has passed through the transport roller such that the previous sheet and the next sheet are prevented from being double fed. That is, JP-A-2005-96450 discloses a configuration in which the driving of the transport roller is stopped until the previous sheet has been transported to a position for preventing double feeding, and the transport roller is then driven. Thereafter, when the previous sheet is transported, the next sheet is transported by the same transport amount as the feed amount of the previous sheet.
However, JP-A-2005-96450 does not disclose detailed motor control for ensuring a gap exists between the previous sheet and the next sheet. The plurality of motors for separately driving the plurality of transport rollers need to be controlled to cooperate with one another in order to suitably transport the sheet. For example, in JP-A-2005-96450, the driving of the transport roller is stopped until the previous sheet has been transported to the position for preventing double feeding, and the transport roller is then driven. In this case, a motor (first motor) for driving an upstream transport roller (first transport roller) which is stopped until the transport of the next sheet starts and a motor (second motor) for driving a downstream transport roller (second transport roller) which transports the previous sheet to the position for preventing double feeding need to be controlled to cooperate with each other. In this case, the first motor is driven at a predetermined timing delayed from a driving start timing of the second motor.
When a sheet is transported in a state in which the sheet is nipped by the first transport roller and the second transport roller, if the start timings of the first motor and the second motor are identical to each other, excessive tension may occur in the nipped sheet such that the sheet is damaged. In order to solve this problem, the first motor is to be driven first and the second motor is driven at a predetermined timing delayed from the driving start timing of the first motor such that the sheet is loosely transported. When the plurality of transport rollers for transporting the sheet are controlled to cooperate with each other by the motors, which of the motors is to be driven first is determined according to a condition and a difference between the timings varies according to the condition. Thus, the control operation becomes complicated. Accordingly, there is a need for a motor control method capable of transporting a sheet by a relatively simple control even when any one of the first motor and the second motor is to be driven first according to the condition.